A device of this kind has in general a torque input element, a torque output element, and elastic members mounted between the torque input element and the torque output element and acting oppositely to the rotation of the torque input element and the torque output element with respect to one another.
When the torque transmission device is of the long travel damper (LTD) type, it comprises several groups of elastic members, the elastic members of a single group being arranged in series by means of a phasing member, so that the elastic members of each group deform in phase with one another.
Conventionally, the torque input element and the torque output element have first and second stop means limiting their relative rotation in two opposite rotation directions, the torque input element and phasing member having third and fourth stop means limiting their relative rotation in two opposite rotation directions.
In this configuration, no means is provided for limiting the angular travel of the phasing member with respect to annular web elements that, for example, makes up the respective torque input and output elements.
In order to improve damping and to absorb vibrations and rotational irregularities of the engine, provision can be made to mount pendulum masses on the phasing member. In this instance said member can exhibit a very large inertia, so that in operation it can completely compress the elastic members in both the “forward” rotation direction and in the opposite, “reverse” rotation direction. The forward direction corresponds to the operating instance in which torque is transmitted from the torque input element to the torque output element. In certain operating phases, for example when the user abruptly lifts his or her foot off the accelerator, a resistance torque is transmitted from the torque output element to the torque input element, which can cause the phasing member to rotate in the reverse direction.
When the elastic members are helical compression springs, excessive compression of said springs can bring the turns into contact with one another. The turns are then said to be “contiguous.” If the torque being transmitted is high, the turns experience crushing, causing fatigue and premature wear on the springs.
In general, it is necessary to be able to limit angular deflections among all the movable elements of the torque transmission device, which is not achieved in the existing art.
The document U.S. Pat. No. 8,047,922 discloses a torsion damper having torque input elements and torque output elements between which are arranged several groups of elastic members arranged in series by means of a phasing member. Stops are provided between the torque input element on the one hand and the phasing member or annular web on the other hand.
A damper of this kind has a relatively complex structure and does not allow the aforementioned problems—of controlling deflection and/or of damage to the springs—to be solved.